Fatal disease spreads to larch trees in Wales

10 JUNE 2010NEWS RELEASE No: 13676

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Forestry Commission Wales experts are working to contain an outbreak of Phytophthora ramorum (P. ramorum) infection in Japanese larch trees in South Wales.

P. ramorum is a fungus-like pathogen that kills many of the trees that it infects. It was found on Japanese larch trees in South West England last year, and the outbreak in woodlands in the Afan Valley, near Port Talbot, Garw Valley, near Bridgend, and the Vale of Glamorgan is the first time it has been encountered on larch elsewhere in Great Britain.

Richard Siddons, Head of Grants and Regulations for Forestry Commission Wales, said,

"Like any threat to our trees, woods and forests, finding Phytophthora ramorum on Japanese larch in South Wales is a worrying development.

"The disease was discovered here as a result of aerial surveys, with subsequent inspections and testing of samples confirming that there is widespread infection in all ages of Japanese larch.

"So far in Wales, it has only been found in woodland that is managed by Forestry Commission Wales on behalf of the Welsh Assembly Government.

"However, the situation is changing rapidly as we undertake more surveys, and it is likely that the infection has spread more widely.

"We are determined to minimise the impacts of this disease on woodlands, and the support of woodland owners in looking out for early signs of infection will play a key part in achieving that."

Until last year, fewer than 100 trees had been infected in Britain since P. ramorum was first identified here on a viburnum plant in a nursery in 2002. Since then, it has mostly affected shrub species such as rhododendron and viburnum, and also bilberry, an ecologically important ground-cover plant common in British woodlands and heathland.

The discovery of the disease on larch in South West England in 2009 was the first time in the world that a commercially grown conifer species had been found with P. ramorum infection. Acting on scientific advice, Forestry Commission England instigated a programme of felling infected trees and a range of biosecurity measures.

A similar programme of actions is now underway in Wales, with biosecurity measures in place to minimise the spread of infection in soil or on larch needles, people, vehicles, equipment and timber.

Extensive felling of affected larch trees in South Wales is about to begin and Forestry Commission Wales is working with timber processors and others to ensure biosecurity measures are put in place to allow logs from the infected trees to be taken to mills for conversion into timber.

Richard Siddons said Forestry Commission Wales is treating the outbreak in South Wales very seriously.

"Together with colleagues in our Forest Research Agency, Fera and the Welsh Assembly Government, we have moved quickly to determine the exact extent of the infected area and to take steps to prevent it from spreading further.

"We are appealing to everyone who works in or visits the affected forests to help us by observing some sensible biosecurity precautions so that they don’t inadvertently spread the pathogen on their boots, bicycle or vehicle wheels, tools or machinery. People are being advised what to do by signs at forest entrances.

"Based on our scientists’ knowledge of regional weather patterns and how the disease spreads in mists, rain and air currents, we hope that we can contain it within the South West of England and South Wales, in a region bounded in the north roughly by the A44 road in mid Wales and in the east by the M5 motorway."

Further information about P. ramorum is contained in a question and answer factsheet on the Forestry Commission’s website at www.forestry.gov.uk/pramorum.

Photo caption: young Japanese larch tree killed by Phytophthora ramorum

NOTES TO EDITORS

Phytophthora ramorum

Phytophthora ramorum (P. ramorum) is a ‘quarantine’ organism under European Union law and its presence on trees or woodland plants must be notified to the relevant authorities (Forestry Commission, Fera, Welsh Assembly Goverment, Scottish Government). It was first found in Britain on a viburnum plant in a nursery in 2002.

P. ramorum causes the disease known as "sudden oak death" in the USA, where it has killed millions of American native oak and tanoak trees. However, its American nickname is a misnomer in Britain, where laboratory tests have shown that our two native species of oak, sessile and pedunculate oak, are much more resistant to P. ramorum than their American cousins. Fewer than five native oak trees have been confirmed with P. ramorum infection in Britain.

It should not be confused with acute oak decline (AOD), which is a separate disease affecting oak trees in the Midlands and parts of Wales and South East England, and in which a newly discovered bacterium species appears to be involved.

P. ramorum kills most trees that it infects, but symptoms vary according to the type of tree or shrub. On Japanese larch (Larix kaempferi) trees, it causes shoot tips to wilt and needles to turn black and fall prematurely. Numerous cankers that bleed resin can appear on branches and the upper trunk. Infected Japanese larch trees produce particularly high numbers of the spores that spread the disease – five times the level produced on rhododendron - meaning the disease can quickly affect a large number of trees and shrubs.

P. ramorum has not been found infecting any European larch (Larix decidua) or hybrid larch (Larix x eurolepsis) trees, which are the other two species of larch grown in Britain, but these species are being kept under close surveillance.

P. ramorum can be spread on footwear, vehicle wheels, tools and machinery that have been used in infected forests, or by the movement of infected plants. It can also be spread in rain, mists and air currents, and scientists at Forest Research, the Forestry Commission’s scientific research arm, believe this is the likely pathway for the Japanese larch infections from South West England to South Wales.

In South West England, P. ramorum has affected a mix of Forestry Commission and privately owned forests.

P. ramorum has not been found on any trees in Scotland.

Japanese larch

Complete figures are not available for Japanese larch numbers alone, but all three larch species together cover an estimated 134,000 hectares in Britain, or about 5 per cent of total woodland. Individual country figures are:

· Wales – 23,000ha / 8 per cent;

· England – 43,000ha / 4.3 per cent;

· Scotland – 65,000 ha / 5.1 per cent.

(To convert hectares to acres, multiply by 2.47)

Larch is a durable, versatile timber that tolerates changes between wet and dry conditions very well, and resists rotting when used in the ground. It is therefore in demand for outdoor uses such as fence posts, fence panels, exterior wall cladding, boats, sheds and furniture, as well as indoor uses such as flooring and chipboard. It is easily stained, worked and finished.

Advice to woodland owners or managers

Woodland owners or managers who suspect infection in their trees should report it to:

Photographs are available on request from the media contacts above. These include views of infected trees, close-ups of diseased needles and shots of staff taking biosecurity measures such as disinfecting their boots.